1. Field of the Invention
The present invention relates to a print control method for detecting and deleting the black frame which appears around a positive image area obtained from a negative microfilm, and an apparatus suitable for this control method.
2. Prior Art
In a negative microfilm, a transparent area without an image is creaked to surround an image area of an original copy. When the image of the original copy is printed out, it is necessary to output an area larger than the original copy so that the entire area of the original copy does not go beyond the output area.
FIG. 9 shows the relationship between the microfilm and the print output. Original copy images 12, 14 are recorded or photographed on the microfilm 10 at a predetermined or given size as negative images. Since the area 16 to be enlarged and projected onto a screen is predetermined, black frames 22, 24 appear outside print images 12A, 14A of the images 12, 14 respectively when the entire image of the area 16 is reversed to, and printed as, positive images.
Methods for automatically detecting and masking these black frames 22, 24 have been proposed. In one of the prior methods, an image is read by a line sensor on respective scanning lines 26 at a predetermined interval (for example, 1 mm). If image signals continuously provide black pixels at a predetermined number of N (for example, 224), such portion is determined as the black frames 22, 24. The predetermined number N=224 is, for example, a length corresponding to 14 mm on the original copy or document.
As shown in FIG. 9, this prior method detects a coordinate x where N black pixels continue, from a coordinate X where the distribution of pixels on the scanning line 26 changes from white pixels to black pixels, and determines the coordinate X=x-N, which is the coordinate traced back from the coordinate x by N pixels, as a coordinate of a peripheral portion of the black frame. Then, similarly, the peripheral coordinates of black frame X.sub.n, X.sub.n+1, X.sub.n+2, .... are sequentially found for the n-th, (n+1)-th, (n+2)-th .... scanning lines 26 at a predetermined interval (for example, 1 mm) to find the region of the black frame or the masking frame connecting each peripheral coordinate of X.sub.n, X.sub.n+1, X.sub.n+2,
In the present specification, a black frame means a frame margin other than an image which appears when a projected image (negative image) is reversed to make it a positive image, and in which black pixels constitute the black frame. In the negative image before negativepositive reversal, portions other than the image appear as a transparent (or white) frame, while black pixels appear as white ones. In this specification, such portions other than the image are called a black frame regardless of negative-positive reversal, and pixels constituting such a black frame are called black pixels.
A conventional apparatus projects a frame of the microfilm on a screen with a magnification which enlarges it to the original size of the original copy (hereinafter called a restore magnification), and detects the black frame by using the enlarged image appearing on the screen. Then, it reads the enlarged image projected on the screen with a line sensor, which moves behind the screen, and outputs to a printer for printout in the same size as the original copy after removing the black frame from the thus read image.
On the other hand, the microfilm is shot with frames of a prescribed size at a fixed interval. However, since the size of the screen on which a predetermined area is read from the recorded microfilm and displayed is predetermined, there may arise a situation in which a plurality of projected images are contained in the display area of the screen, or where part of an image extends outside of the display area, depending on the stopping position of the microfilm. In addition, depending on the type of microfilm, a plurality of a small original copies or documents such as bank bills or checks, or the front and back sides thereof are shot or photographed in one frame. In such a case, a plurality of document images are contained in one display area.
FIGS. 4 (A) and 5 (A) show the relationship between the microfilms 10A, 10B and the enlarged projection area 16A, 16B of the screen, respectively. In FIG. 4 (A), for example, reduced images 12C, 12D of an A-4 size original documents are photographed in the microfilm 10A, and part of one image 12D is out of the area 16A on the screen on which it is enlarged and projected. Here, the projection area 16A on the screen is assumed to be A-3 size.
In addition, the microfilm 10B shown in FIG. 5 (A) contains images 12E, 12F .... of the front side and those 12e, 12f, .... of the back side of a draft or check. The projection area 16B of an A-3 size screen, for example, contains a plurality of these document images.
As described above, since an image magnified by the restore magnification is projected onto the screen, the size of the display area of the screen is determined to be of a size necessary and sufficient to contain the image at the restore magnification. However, to prevent the apparatus from becoming too large, the screen cannot be made too large with regard to the recovered size. In addition, if the screen is too small, a portion of the projected image falls beyond the display area of the screen when the position of the projected image is shifted or inclined from the normal position. Moreover, when a plurality of document images are contained in the projection and display area of the screen, an unnecessary document image or an image having a missing part is output to a printer or the other external device even if the black frame is removed as described.
It is also conceivable to print an image by removing the unnecessary image portion or the image portion having a missing part. In this case, however, if it is printed out at the same size (for example, A-3 size) as the areas 16A, 16B which are enlarged and projected onto the screen, a large blank area is produced surrounding the document images (for example, 12C, 12f) on the print paper 18A, 18B as shown in FIGS. 4 (B) and 5 (B).
Furthermore, it is desirable to print out images on paper with the same size for convenience of filing. In this case, if the size of the images to be printed is not standardized, the print out may be poor in appearance since a large blank zone is produced around the image or a part of the image may not be recorded on the paper.